Premixed compression ignition diesel engine

ABSTRACT

In a premixed compression ignition diesel engine  1  with fuel being injected midway of a intake passage  15,  an intake port  6  is formed with an orifice  10  which is throttled in passage cross-sectional area at least in an opening operation of an intake valve  7.  This prevents adhesion of the fuel to an inner wall of the intake passage and promotes atomization of the fuel. A combustion chamber is fed with the sufficiently atomized fuel, which prevents combustion failure in the combustion chamber to attain reduction of particulate matters.

TECHNICAL FIELD

The present invention relates to a premixed compression ignition dieselengine.

BACKGROUND ART

In general, a diesel engine as internal combustion engine employs notplug spark ignition like a gasoline engine but natural ignition throughdirect injection of light oil as fuel into air which has beenhigh-temperatured through high compression.

For a diesel engine, attention is recently paid to a so-called premixedcompression ignition strategy for injection of fuel at high pressure andbefore a top dead center of a piston stroke so as to premix the fuelwith air, the fuel-air mixture being compressed into high temperature tocause autoignition and combustion in a single burst.

In order to implement the premixed compression ignition strategy, adiesel engine with fuel such as light oil being injected midway of anintake passage is being developed.

State-of-the-art technology for a premixed compression ignition enginewith fuel being injected midway of an intake passage is disclosed, forexample, in Patent Literature 1.

Patent Literature 1: JP 2007-24001A

SUMMARY OF INVENTION Technical Problems

However, the above-mentioned injection of the fuel such as light oilinferior in evaporation characteristics to gasoline midway of an intakepassage may bring about adhesion of the oil to an inner wall of theintake passage. The adherent fuel directly flows into a combustionchamber in a cylinder, so that the combustion chamber is fed with theinsufficiently atomized fuel, resulting in possible combustion failurein the combustion chamber and thus production of a lot of particulates(particulate matters), which requires improvement.

The invention was made in view of the above and has its object toprovide a premixed compression ignition diesel engine capable ofpreventing fuel from adhering to an inner wall of an intake passagewhile promoting atomization thereof, feeding sufficiently atomized fuelto a combustion chamber and preventing combustion failure in thecombustion chamber to attain reduction of particulates.

Solution to Problems

The invention is directed to a premixed compression ignition dieselengine with fuel being injected midway of an intake passage, comprisingan orifice formed in an intake port which is throttled in passagecross-section area at least in an opening operation of an intake valve.

According to the above-mentioned means, the following actions may beacquired.

With the above-mentioned construction, when fuel such as light oil isinjected midway of the intake passage and even if the fuel such as lightoil adheres to the inner wall of the intake passage, the adherent oildoes not directly flow into the combustion chamber in the cylinder andis atomized by the fuel-air mixture with a flow rate increased whenpassing through the orifice formed in the intake port; as a result, thecombustion chamber is fed with the sufficiently atomized fuel, resultingin less possible combustion failure in the combustion chamber to attainreduction of particulates.

In the premixed compression ignition diesel engine, the orifice maycomprise a thick portion swellingly formed on an interior of the intakeport at a location surrounding a valve stem of an intake valve and alarge-diameter portion formed on the valve stem so as to face the thickportion at least in an opening operation of the intake valve.

In this case, the thick portion of the orifice may be provided with afuel injecting means which injects fuel into the intake port. Thiscauses the fuel to be sucked from the fuel injecting means into theintake port due to the ejector effect, so that there is no necessity ofproviding a special fuel injection nozzle or the like midway of theintake passage; with the simple construction, the fuel may be preventedfrom adhering to the inner wall of the intake passage and theatomization thereof may be promoted.

The fuel injecting means may comprise injection ports opened at aplurality of positions circumferentially of the thick portion.

The fuel injecting means may comprise an annular injection slot openedthroughout the circumference of the thick portion.

The fuel injecting means may comprise a porous sintered metal ringmember attached to the thick portion.

Advantageous Effects of Invention

A premixed compression ignition diesel engine according to the inventioncan have meritorious effects that fuel is prevented from adhering to aninner wall of an intake passage while promoting atomization thereof,that sufficiently atomized fuel is fed into a combustion chamber andthat combustion failure in the combustion chamber is prevented to attainreduction of particulates.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic section of a first embodiment of the invention;

FIG. 2 is a schematic section of a second embodiment of the invention;and

FIG. 3 is a schematic section of a third embodiment of the invention.

Reference Signs List

1. diesel engine2. cylinder3. piston4. combustion chamber5. cylinder head6. intake port7. intake valve7 a. valve stem7 b. large-diameter portion10. orifice11. thick portion12. fuel injecting means12 a. injection port12 b. fuel feed port12 c. annular fuel header passage12 d. annular injection slot12 e. porous sintered metal ring member13. intake pipe15. intake passage

DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described with reference to thedrawings.

FIG. 1 shows a first embodiment of the invention in which referencenumeral 1 denotes a diesel engine; 2, a cylinder in the diesel engine 1;3, a piston slidably inserted in the cylinder 2; 4, a combustion chamberformed at a top of the piston 3 in the cylinder 2; 5, a cylinder head onan upper portion of the cylinder 2; 6, an intake port formed in thecylinder head 5; 7, an intake valve which opens/closes the intake port6; 8, an exhaust port formed in the cylinder head 5; and 9, an exhaustvalve which opens/closes the exhaust port 8. The intake port 6 is formedwith an orifice 10 which is throttled in passage cross-section area atleast in an opening operation of the intake valve 7. The orifice 10comprises a thick portion 11 swellingly formed on an interior of theintake port 6 at a location surrounding a valve stem 7 a of the intakevalve 7 and a large-diameter portion 7 b formed on the valve stem 7 a soas to face the thick portion 11 at least in an opening operation of theintake valve 7. The thick portion 11 of the orifice 10 is provided withfuel injecting means 12 which injects fuel into the intake port 6.

In the first embodiment, the fuel injecting means 12 comprises injectionports 12 a opened at a plurality of positions (e.g., on the order ofthree to eight positions) circumferentially of the thick portion 11. Thefuel injection ports 12 a are fed with fuel from a fuel feed port 12 bthrough an annular fuel header passage 12 c.

In the figure, reference numeral 13 designates an intake pipe connectedto the intake port 6; and 14, an exhaust pipe connected to the exhaustport 8. The intake pipe 13 and the intake port 6 provide an intakepassage 15; and the exhaust pipe 14 and the exhaust port 8 provides anexhaust passage 16.

A mode of operation of the first embodiment will be described.

When the intake valve 7 is opened as indicated by imaginary lines from astate shown by a solid line in FIG. 1, intake air is sucked from theintake pipe 13 and the intake port 6 of the intake passage 15 into thecombustion chamber 4. Feeding of fuel such as light oil at this timingfrom the fuel feed port 12 b of the fuel injecting means 12 through theannular fuel header passage 12 c to the injection ports 12 a bringsabout suction of the fuel from the injection ports 12 a to the orifice10 in the intake port 6 due to an ejector effect and causes the fuel tobe atomized by the intake air with a flow rate increased when passingthrough the orifice 10. As a result, the combustion chamber 4 is fedwith the sufficiently atomized fuel, resulting in less possiblecombustion failure in the combustion chamber 4 to attain reduction ofparticulates.

Moreover, in the first embodiment, since the thick portion 11 of theorifice 10 is provided with the injection ports 12 a for injection offuel into the intake port 6, the fuel is sucked into the intake port 6from the injection ports 12 a due to the ejector effect, so that thereis no necessity of arranging a special fuel injection nozzle or the likemidway of the intake passage 15. Thus, with the simple construction, thefuel may be prevented from adhering to the inner wall of the intakepassage 15 while promoting atomization thereof.

Thus, the fuel may be prevented from adhering to the inner wall of theintake passage 15 while the atomization thereof may be promoted; as aresult, the combustion chamber 4 may be fed with the sufficientlyatomized fuel and combustion failure in the combustion chamber 4 may beprevented to attain reduction of particulates.

FIG. 2 shows a second embodiment of the invention in which parts similarto those in FIG. 1 are represented by the same reference numerals.Although its basic construction is equivalent to that shown in FIG. 1,the second embodiment is characteristic in that the fuel injecting means12 comprises an annular injection slot 12 d opened throughout thecircumference of the thick portion 11, fuel being fed to the annularinjection slot 12 d from the fuel feed port 12 b through the annularfuel header passage 12 c and the injection port 12 a as shown in FIG. 2.

In the embodiment shown in FIG. 2, when the intake valve 7 is opened asindicated by imaginary lines from a state shown by a solid line, intakeair is sucked from the intake pipe 13 and the intake port 6 of theintake passage 15 into the combustion chamber 4. Feeding of fuel such aslight oil at this timing from the fuel feed port 12 b of the fuelinjecting means 12 through the annular fuel header passage 12 c and theinjection ports 12 a to the annular injection slot 12 d brings aboutsuction of the fuel from the annular injection slot 12 d to the orifice10 in the intake port 6 due to the ejector effect and causes the fuel tobe atomized by the intake air with a flow rate increased when passingthrough the orifice 10. As a result, the combustion chamber 4 is fedwith the sufficiently atomized fuel, resulting in less possiblecombustion failure in the combustion chamber 4 to attain reduction ofparticulates.

Moreover, in the second embodiment, since the thick portion 11 of theorifice 10 is provided with the annular injection slot 12 d forinjection of fuel into the intake port 6, the fuel is sucked into theintake port 6 from the annular injection slot 12 d due to the ejectoreffect, so that there is no necessity of arranging a special fuelinjection nozzle or the like midway of the intake passage 15. Thus, withthe simple construction, the fuel may be prevented from adhering to theinner wall of the intake passage 15 while atomization thereof may bepromoted.

Thus, also in the embodiment shown in FIG. 2, the fuel may be preventedfrom adhering to the inner wall of the intake passage 15 while theatomization thereof may be promoted; as a result, the combustion chamber4 may be fed with the sufficiently atomized fuel and combustion failurein the combustion chamber 4 may be prevented to attain reduction ofparticulates as in the case of the embodiment shown in FIG. 1.

FIG. 3 shows a third embodiment of the invention in which parts similarto those in FIG. 1 are represented by the same reference numerals.Although its basic construction is equivalent to that depicted in FIG.1, the third embodiment is characteristic in that the fuel injectingmeans 12 comprises a porous sintered metal ring member 12 e attached tothe thick portion 11, fuel being fed to the porous sintered metal ringmember 12 e from the fuel feed port 12 b through the annular fuel headerpassage 12 c and the injection ports 12 a as shown in FIG. 3.

In the embodiment shown in FIG. 3, when the intake valve 7 is opened asshown by imaginary lines from a state shown by a solid line, intake airis sucked from the intake pipe 13 and the intake port 6 of the intakepassage 15 into the combustion chamber 4. Feeding of fuel such as lightoil at this timing from the fuel feed port 12 b of the fuel injectingmeans 12 through the annular fuel header passage 12 c and the injectionports 12 a to the porous sintered metal ring member 12 e brings aboutsuction of the fuel from the porous sintered metal ring member 12 e tothe orifice 10 in the intake port 6 in a leaching manner due to theejector effect and causes the fuel to be atomized by the intake air witha flow rate increased when passing through the orifice 10. As a result,the combustion chamber 4 is fed with the sufficiently atomized fuel,resulting in less possible combustion failure in the combustion chamber4 to attain reduction of particulates.

Moreover, in the third embodiment, since the thick portion 11 of theorifice 10 is provided with the porous sintered metal ring member 12 efor injection of fuel into the intake port 6 in a leaching manner, thefuel is sucked into the intake port 6 from the annular injection slot 12d due to the ejector effect, so that there is no necessity of arranginga special fuel injection nozzle or the like midway of the intake passage15. Thus, with the simple construction, the fuel may be prevented fromadhering to the inner wall of the intake passage 15 while atomizationthereof may be promoted.

Thus, also in the embodiment depicted in FIG. 3, the fuel may beprevented from adhering to the inner wall of the intake passage 15 whilethe atomization thereof may be promoted; as a result, the combustionchamber 4 may be fed with the sufficiently atomized fuel and combustionfailure in the combustion chamber 4 may be prevented to attain reductionof particulates as in the case of the embodiments shown in FIGS. 1 and2.

Although the fuel injecting means 12 is provided on the thick portion 11of the orifice 10 in all of the three embodiments, the fuel injectingmeans 12 may be provided midway of the intake pipe 13 or at a requiredlocation of the intake port 6 constituting the intake passage 15instead. When the injection is performed midway of the intake passage 15with the fuel injecting means 12 provided midway of the intake pipe 13or at a required location of the intake port 6 constituting the intakepassage 15 and even if the fuel such as light oil adheres to the innerwall of the intake passage 15, the adherent oil does not directly flowinto the combustion chamber 4 in the cylinder and is atomized by afuel-air mixture with a flow rate increased when passing through theorifice 10 formed in the intake port 6; as a result, the combustionchamber 4 is fed with the sufficiently atomized fuel, resulting in lesscombustion failure in the combustion chamber 4 to attain reduction ofparticulates.

It is to be understood that a premixed compression ignition dieselengine according to the invention is not limited to the aboveembodiments and that various changes and modifications may be madewithout departing from the scope of the invention.

1. A premixed compression ignition diesel engine with fuel beinginjected midway of an intake passage, comprising an orifice formed in anintake port which is throttled in passage cross-section area at least inan opening operation of the intake valve.
 2. A premixed compressionignition diesel engine as claimed in claim 1, wherein said orificecomprises a thick portion swellingly formed on an interior of the intakeport at a location surrounding a valve stem of the intake valve and alarge-diameter portion formed on said valve stem so as to face saidthick portion at least in an opening operation of said intake valve. 3.A premixed compression ignition diesel engine as claimed in claim 2,wherein said thick portion of said orifice is provided with fuelinjection means which injects fuel into the intake port.
 4. A premixedcompression ignition diesel engine as claimed in claim 3, wherein saidfuel injection means comprises injection ports at a plurality ofpositions circumferentially of the thick portion.
 5. A premixedcompression ignition diesel engine as claimed in claim 3, wherein saidfuel injection means comprises an annular injection slot openedthroughout the circumference of the thick portion.
 6. A premixedcompression ignition diesel engine as claimed in claim 3, wherein saidfuel injection means comprises a porous sintered metal ring memberattached to the thick portion.